1. Field of the Invention
The present invention relates to surface connection for establishing an electric connection between a pair of printed circuit boards.
2. Description of the Prior Art
A multilayered printed circuit board is well known, which comprises layers of wiring patterns embedded in a substrate. Such a printed circuit board usually allows only input/output contact pads to expose at the surface of the substrate. On the other hand, a wiring pattern cannot be embedded in a substrate of some printed circuit boards such as flexible printed circuit boards, since such printed circuit boards cannot contain a large number of layers. A wiring pattern should be exposed at the surface of the substrate. The wiring pattern is covered with a protection film on the surface of the substrate.
In general, a connector is employed when an electric connection is to be established between the flexible printed circuit board and other circuit boards. Such a connector comprises a plug component mounted on either of the boards and a receptacle component mounted on the other of the boards. When the plug component is received in the receptacle component, a contact pin on the plug component enters a contact socket on the receptacle component. Electric connection can be established between the contact pin and socket. Combinations of pins and sockets are allowed to provide a large number of signal channels in a single connector.
The contact pins and sockets are supported in housings of synthetic resin material, respectively. The housings serve to electrically insulate the adjacent contact pins and sockets from each other. However, such housings are supposed to hinder reduction in size of the plug and receptacle components.
It is accordingly an object of the present invention to provide a connecting mechanism capable of establishing an electric connection between a pair of printed circuit boards in a smaller space.
According to the present invention, there is provided an electronic apparatus comprising: a first and a second printed circuit board; a conductive pattern formed on a surface of a substrate in at least one of the first and second printed circuit boards; a protection film formed on the substrate so as to cover over at least partly the conductive pattern; and an elastic conductive member interposed between the first and second printed circuit boards.
With this structure, the elastic conductive member is employed to establish an electric connection between the first and second printed circuit boards in place of, for example, a prior art connector comprising a plug and a receptacle component. The elastic conductive member may comprise a plurality of brass wires penetrating through an elastic insulation plate made of silicon. The wires are designed to establish signal channels between the first and second printed circuit boards. Since the brass wires can be made short, the space between the first and second printed circuit boards can be suppressed even when the elastic conductive member is interposed between the first and second printed circuit boards. Accordingly, an electric connection can be established between a pair of printed circuit boards in a smaller space.
In order to realize the aforementioned electronic apparatus, a printed circuit board may comprise: a substrate; a conductive pattern formed on a surface of the substrate; a protection film formed on the substrate so as to cover over at least partly the conductive pattern; and a conductive contact protruding from a surface of the conductive pattern so as to reach a level above a surface of the protection film.
For example, a conventional anisotropic conductive rubber plate may comprise a plurality of brass wires uniformly arranged over the entire area of an elastic insulation plate. When the anisotropic conductive rubber plate has been interposed between a pair of printed circuit boards, the brass wires are arranged not only at a location aligned with the contact pads for establishing signal channels in the conductive pattern but also at a location off the contact pads. If the protection film covers over the conductive pattern off the contact pads, the brass wires cannot reach the contact pads because the brass wires off the contact pads first contact the protection film so as to hinder the brass wires from approaching the contact pads. An electric connection cannot be established between the brass wires and the contact pads.
On the other hand, the electronic apparatus of the present invention may employ a conductive contact protruding from a surface of the conductive pattern so as to reach a level above a surface of the protection film. The conductive contact in this manner is adapted to allow the brass wires to first contact the conductive contact when the anisotropic conductive rubber plate is superposed on the printed circuit board. The protection film surely fails hinder establishment of signal channels leading from the conductive pattern to the brass wires. Such conductive contact may comprise a contact pad shaped in the conductive pattern, and a solder bump formed on a surface of the contact pad. Otherwise, the conductive contact may be integrated with the conductive pattern.
In order to realize the aforementioned electronic apparatus, an elastic conductive member may comprise: an elastic insulation plate defining through holes; and a conductive pin selectively received in the through hole. This type of elastic conductive member allows the conductive pin to be selectively arranged only at location aligned with the conductive pattern exposed at the breaks of the protection film. Such conductive pin is allowed to first contact the conductive pattern without inducing collision against the protection film when the elastic conductive member is superposed on the surface of the printed circuit board. The elastic conductive member serves to reliably establish a signal channel leading from the conductive pattern to the conductive pin.
The elastic conductive member may employ an insulation plate defining an operative through hole only for receiving the conductive pin. Otherwise, an insulation plate may define, in addition to the operative through hole, an additional or inoperative through hole of a diameter identical to that of the operative through hole. Employment of such an inoperative through hole is designed to allow the conductive pin to be relocated from the operative through hole to the inoperative through hole. Accordingly, the elastic conductive member is allowed to easily change the pattern of electric connection between a pair of printed circuit boards. The through holes uniformly arranged in a larger area enable any combination of the operative through holes, so that the elastic conductive member is allowed to deal with the contact pads in various arrangement without redesigning the insulation plate and the conductive pin. In producing the insulation plate, it is not necessary to distinct the operative and inoperative through holes from each other, since the operative and inoperative through holes have the same dimension.
The present invention may be applied to any types of printed circuit boards assembled within an electronic apparatus such as a computer hardware, a PDA (personal digital assistant), and the like.